A062784 Numbers k such that sigma(k) + phi(k) is a perfect square.

2, 4, 56, 110, 125, 161, 287, 391, 418, 423, 511, 588, 609, 675, 721, 799, 910, 935, 1048, 1057, 1102, 1130, 1281, 1351, 1457, 1485, 1630, 1716, 1799, 1826, 1921, 2047, 2060, 2177, 2255, 2378, 2403, 2449, 2457, 2472, 3199, 3266, 3915, 4010, 4376, 4417

Offset: 1

Author

Jason Earls, Jul 18 2001

Keywords

• nonn

Links

• Harry J. Smith, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A065387.

Programs

Mathematica

Select[Range[4500],IntegerQ[Sqrt[DivisorSigma[1,#]+EulerPhi[#]]]&] (* Harvey P. Dale, Jan 18 2012 *)

PARI

select(k->issquare(sigma(k) + eulerphi(k)), [1..5000])